this looks like a box you plug your controller into and it converts the signals and pumps the data out over a rather high speed (relatively) transceiver. and a box at the other end that goes into the console. id prefer to put all the electronics for the receiver into the controller itself. instead of let the mcu on the board convert button presses to a serial signal, and then encapsulate that into a packet for transmission over a transciever, as what these diagrams seem to indicate. id just cut out the middle man, use a single mcu to read the buttons directly, transmit their states over the transceiver, and just have the mcu at the other end pretend to be an snes controller, receiving state data from the unit in the controller.
what i would do is just design the boards in a cad program, and make them yourself / have them made. there are services who will fabricate pcbs to spec for you, but they cost $$$. you can do it yourself if you have the equip (blank pcbs, laser printer, ferric chloride, drill press, router table, etc). im still trying to score a laser printer for cheap, and a dremel is about all you need for drilling/routing (i can do it freehand). you can probably hand solder smd parts (like chips with gull wing contacts), to allow any chips you need to be as small as possible. as opposed to using a transceiver module i would just get the transceiver chip and a chip antennae, and include it on the same board. its an smd, in a rather hard to solder package so have fun there.
the transceiver they are using is something ive been looking at. i just ordered a pair of them from china a few days ago for the ridiculously low price of $6.40 (and they even paid the shipping). they normally go for a lot more.
the module is about the size of a quarter, and il be sure to tell you about them when i get em in the mail in a couple weeks. you might be able to cram it into the controller if you used smd parts for everything else. they will be better than the ask modules ive been using, which work, when they want to.
as for the diagrams, they come with the hex files which is the program you run on the mcu, but i would prefer to have actual source code for tweaking. as for me, i would just pay the $2 for the usb gamepad and play it on my emulator. my gamepad conversion was more or less meant for radio control applications and less for gaming (its not responsive enough for that).